Spurious? Brake Pad Warning Light

Discussion in 'Tech/Mech General' started by billkce, Sep 25, 2013.

  1. billkce

    billkce Funster

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    Here's another poser from deepest Italy. Merc Sprinter 313cdi

    Coming down long, steep hills outside Innsbruck & Lake Garda, the Brake Pad Warning lite came on. We were applying moderately heavy braking over 10 minutes. After stopping for 10 minutes & restarting, it was out. No reappearance on level roads. Brakes seemed OK.

    We got an Italian mechanic to check all 4 discs & pads. All new, as we expected. No damage. So, he topped up the brake fluid & sent us on our way.

    However, en route St Tropez, lite reappeared going downhill on the A8 near Cannes. No problem braking. Lite out after restart.

    Anyone got a suggestion as to why this might be happening? Can warm brakes set the pad sensor off? Can the float in the brake fluid reservoir be exposed on steep descents & cause the lite?

    Any help gratefully accepted.:thumb:

    Kind regards

    Billkce
     
    Last edited: Sep 25, 2013
  2. jonandshell

    jonandshell Funster

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    Not sure about your light. I suppose its a possibility that a hot nrake pad might be more conductive causing the lamp to illuminate.
    What is more likely is that the probe in the pad is floating about after the resin that holds it has melted with the heat!
    Have you thought of using engine braking for long descents? Cooking your brakes leaves nothing for when you REALLY need them!:Eeek:
     
  3. billkce

    billkce Funster

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    Hi, thanks for response. Mechie checked sensors. OK. Also, I can assure you that I use gears for braking, so I'm not convinced the brakes were that hot. They didn't smell/feel hot after stopping.
     
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  4. jonandshell

    jonandshell Funster

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    That's good to hear! I wonder, when I see people tearing down steep descents with their brake lights on, if they realise that faded brakes don't stop you!!!

    Brake fade was taught on HGV training but overlooked on car lessons. I NEVER rely on brakes for retardation on descents. Right speed, right gear!:thumb:
     
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  5. B-well

    B-well Funster

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    Altitude and brake fade work together, sounds like possible heat transmitted through brake fluid causing it to boil, when colled down returns to normal, indicators on brakes will do the same.
    you sure it not your step light causing signal ? just a thought.
     
  6. neilydun

    neilydun Read Only Funster

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    New drivers are taught not to use there gears, to slow themselves, just the brakes !
    What a joke !
    My oldest past his test this year, but needed to be shown to use the gears on descents, and approaching lights etc
     
  7. B-well

    B-well Funster

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    Thats because brakes are cheaper to replace than gearboxes.
     
  8. pappajohn

    pappajohn Funster Life Member

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    pad warning light will be link to other brake components as well.

    low/overheating fluid will also bring the light on

    moderate heavy braking for 10 minutes......i'm not surprised it got a tad warm.
     
  9. jonandshell

    jonandshell Funster

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    Scary!

    It is mad not to stay at a safe, engine-controlled speed on long descents! The best friction materials in the world lose friction with excessive heat!

    When descending long hills, all you need to do is stay in a gear which allows you to descend the hill using the compression of the engine to control your speed. Brakes are for stopping and slowing down, not constant speed control!

    Its all down to the terrain ultimately. If you are on a short descent, a dab of the brakes is all that is needed to slow things up, but if you need to brake constantly for miles to control your speed, there is something badly wrong with your driving! You will overheat your brakes, at the least causing excessive wear, at worst lose them completely and have to use the scenery as a brake at the next bend!:Eeek:

    It should be pointed out that brake fluid should be changed regularly on motorhomes. They are heavy beasts that need good brake efficiency. As previously mentioned, brake fluid is hygroscopic. It attracts moisture!
    Brake fluid has a high boiling point, water does not! Water in a hot brake system can boil in the calipers causing steam bubbles and a spongy pedal that could go straight to the floor without applying your brakes!:Eeek:
    Add the reduced friction caused by brake lining overheating, bombing down an Alpine pass in 6th gear, feathering the brakes constantly to control your speed, is a bit suicidal!:Eeek:
     
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  10. jonandshell

    jonandshell Funster

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    Just a thought...............

    Why is someone from Norfolk on here giving advice about driving on steep hills?!!!:Doh:
     
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  11. Allanm

    Allanm Funster

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    In a previous occupation, we used to be able to light cigarettes off glowing red brake discs after a spirited drive when it was considered inappropriate to use engine braking. Brakes still worked fine, but the cars generally went to the garage for a check over and parts were changed when necessary.
    I had 3 sets of discs pads and calipers in a week once. Thank goodness I never had to foot the bill.
    In normal driving, we always used engine braking when descending hills or for when use of the brakes might lock the wheels, this also applied to automatics. If you do it smoothly and gradually, it causes little wear to the gearbox and takes the pressure off the brakes, for when, as Jonandshell quite rightly says, you need to stop.

    Allan
     
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  12. billkce

    billkce Funster

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    Thanks for input re Brake Pad light. I can assure you all, that we use gears for speed control & have very large lorries bombing past us!

    My concern is, that, we have been going up & down hills in the Alpine regions for 4 years now, the brake parts are newish & the light has never come on before. Even when towing a Smart Car on a trailer.

    I'm still puzzled as to why the light should start coming on now?
     
  13. Allanm

    Allanm Funster

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    You said the mechie topped the brake fluid up and sent you on your way. Was the fluid low and is it low again now? It could be something as simple as an over sensitive fluid level sensor. Make sure there is plenty of fluid in the reservoir. I can't think of any other reason the light would come on
    Allan
     
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  14. billkce

    billkce Funster

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    Brake fluid topped up by mechie & no leaks.

    I believe you are right about over sensitive fluid sensor. Thanks, it confirms what another Brit camper I met said. :thumb:
     
  15. TheBig1

    TheBig1 Funster Life Member

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    its all well and good practice to top up brake fluid. but have you replaced it every few years?

    brake fluid absorbs water from the atmosphere and this degrades the efficiency of the brakes, this shows as brake fade and boiling of the water in the fluid. would also cause the brake warning light to come on when you give the brakes a decent workout.

    change the brake fluid to cure
     
  16. Trikeman

    Trikeman Read Only Funster

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    Checked handbrake switch?????
     
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